High power semiconductor light sources such as lasers provide high output power over a relatively narrow optical spectrum. Other semiconductor light sources such as light emitting diodes (LEDs) and superluminescent LEDs provide low output power over a relatively broad optical spectrum. For example, lasers can typically couple about a few milliwatts of power into a single mode optical fiber over a spectrum that consists of discrete longitudinal modes that each have a linewidth of less than one angstrom. Commercially available LEDs, on the other hand, can typically couple only about 100 microwatts into an optical fiber, but over a continuous optical spectrum that is 500-1000 angstroms in width.
A semiconductor light source that operates at high output power over a broad optical spectrum is shown in Goldberg et al., Electron. Lett., 1994, 30, (20), pp. 1682-1684. As seen in FIG. 1 of Goldberg, the output from a superluminescent LED is coupled via a lens into a broad area amplifier.